Thin heating systems are known. Woven wire mesh heaters having no buses are made whereby thin wires are woven into a mesh mat. The mat can be placed under a laminate floor or under a subfloor or placed into non-constructions environments. However, these mats must be custom made to fit odd-sized spaces and cannot be altered at the job site. This increases the cost of the heaters and installation, and makes the process of changing the heater layout during installation significantly more difficult.
Polymer-based heaters are made using electrically resistive plastics. A conductive bus on either side of the resistance heaters completes the circuit. The result is a cuttable heating surface; however currently available products exhibit significant thickness.
Conductive ink-based heaters are made from resistive inks printed on plastic sheets. A conductive bus on either side of the resistance heaters completes the circuit. A second plastic sheet is then placed over the circuit to protect the heating elements. The result is a thin, flexible, cuttable heating surface. Conductive ink-based heaters are known for use under laminate floors, where they lay unattached in the space between the floor boards and the subfloor or, in the case of a remodel, an old floor. The plastic sheets that protect the device provide a poor surface for adhesion of ceramic tiles.
In heating elements formed on plastic sheets, there is some current leakage due to the thin nature of the sheets and capacitive effects. The magnitude of leakage current can reach to unacceptably high levels in wet environments such as in the case of flooring applications in bathrooms and kitchens. Controlling this current leakage, particularly in applications where the heating elements may be subject to high humidity or water can become problematical. The problem of electrical leakage current in wet applications has not been solved to date by the current state-of-the-art electrical and electrical heater technologies.
Damage to the thin plastic sheets could additionally result in an electrical short between some of the current carrying elements, which could also result in an unacceptable condition, such as an electrical shock or overheating of the heating elements or the plastic sheets due to high current flow.